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Emission and dry deposition of accumulation mode particles in the Amazon Basin
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
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2010 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, no 21, 10237-10253 p.Article in journal (Refereed) Published
Abstract [en]

Size-resolved vertical aerosol number fluxes of particles in the diameter range 0.25–2.5 μm were measured with the eddy covariance method from a 53 m high tower over the Amazon rain forest, 60 km NNW of Manaus, Brazil. This study focuses on data measured during the relatively clean wet season, but a shorter measurement period from the more polluted dry season is used as a comparison. Size-resolved net particle fluxes of the five lowest size bins, representing 0.25–0.45 μm in diameter, pointed downward in more or less all wind sectors in the wet season. This is an indication that the source of primary biogenic aerosol particles may be small in this particle size range. In the diameter range 0.5–2.5 μm, vertical particle fluxes were highly dependent on wind direction. In wind sectors where anthropogenic influence was low, net emission fluxes dominated. However, in wind sectors associated with higher anthropogenic influence, net deposition fluxes dominated. The net emission fluxes were interpreted as primary biogenic aerosol emission, but deposition of anthropogenic particles seems to have masked this emission in wind sectors with higher anthropogenic influence. The emission fluxes were at maximum in the afternoon when the mixed layer is well developed, and these emissions were best correlated with horizontal wind speed by the equation log10F=0.47·U+2.26 where F is the emission number flux of 0.5–2.5 μm particles [m−2s−1] and U is the horizontal wind speed [ms−1] at the top of the tower.

Place, publisher, year, edition, pages
2010. Vol. 10, no 21, 10237-10253 p.
National Category
Natural Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-38540DOI: 10.5194/acp-10-10237-2010ISI: 000284210400006OAI: oai:DiVA.org:su-38540DiVA: diva2:310934
Available from: 2010-04-19 Created: 2010-04-19 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Aerosol Exchange between Forests and the Atmosphere: Fluxes over a Tropical and a Boreal Forest
Open this publication in new window or tab >>Aerosol Exchange between Forests and the Atmosphere: Fluxes over a Tropical and a Boreal Forest
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main goal of this thesis was to investigate primary biogenic aerosol emission from the Amazon rain forest through measurements of vertical turbulent aerosol number fluxes. In addition, the particle dry deposition sink has been analysed and quantified, and is also compared with the dry deposition sink at a boreal forest site.

The total aerosol number flux of particles with diameter larger than 10 nm was dominated by downward fluxes at the rain forest site, even in the most pristine conditions in the wet season. This is an indication that the primary biogenic aerosol number source is small when considering the total particle size spectrum. However, size resolved aerosol number fluxes indicated net emission for particles with dry diameter 0.5-2.5 μm in clean conditions. These emission fluxes are likely explained by a primary biogenic aerosol source from the rain forest and seemed to be best correlated with horizontal wind speed, peaking during afternoon. Even though there are few particles in this diameter interval, typically one particle per cm3, they could potentially play an important role as giant nuclei in warm rain initiation.

Average particle number based dry deposition velocities over the whole aerosol population were lower at the rain forest site than at the boreal forest site. The reasons are likely the high fraction of accumulation mode particles at the rain forest site and low wind speeds in the tropics compared to the midlatitudes.

This thesis provides a relation describing emission of particles with diameter 0.5-2.5 μm from the rain forest, as a function of wind speed. In addition, linear equations relating average dry deposition velocity of the total aerosol number population to friction velocity are suggested for both the wet and dry season at the rain forest site. Finally, this thesis provides a relationship between dry deposition velocity of particles within the diameter range 0.25-0.45 μm, friction velocity and particle diameter.

Place, publisher, year, edition, pages
Stockholm: Department of Applied Environmental Science (ITM), Stockholm University, 2010. 42 p.
National Category
Natural Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-38544 (URN)978-91-7447-051-2 (ISBN)
Public defence
2010-05-28, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.Available from: 2010-05-06 Created: 2010-04-19 Last updated: 2011-05-25Bibliographically approved

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Ahlm, LarsKrejci, RadovanNilsson, DouglasMårtensson, MonicaVogt, Matthias
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